Conventionally, in a semiconductor manufacturing process, a plurality of processes such as heat treatment, film formation, etching and the like is performed on a semiconductor wafer (hereinafter, simply referred to as “wafer”) that is a target substrate. Recently, along with a trend toward high integration or miniaturization of semiconductor devices, in order to prevent adhesion of particles to the wafer or oxidation of a surface of the wafer, the wafer is transferred while being accommodated in a sealed type container referred to as a FOUP (Front-Opening Unified Pod) maintained under a clean atmosphere. The FOUP includes a main body for accommodating a plurality of wafers in a horizontal state and a cover for opening/closing the main body.
A substrate processing system for performing a predetermined process on a wafer includes a wafer transfer chamber of an atmospheric pressure (normal pressure) which is referred to as an EFEM (Equipment Front End Module). The wafer transfer chamber is provided at a loading side of the substrate processing system. A wafer is transferred between the FOUP and a processing apparatus of the substrate processing system by a transfer unit in the EFEM.
The EFEM includes a load port for loading a wafer. The FOUP is mounted on the load port. The load port has a door designed based on FIMS (Front-opening Interface Mechanical Standard). When the door moves while being connected to the cover provided at the FOUP, a space in the FOUP communicates with a space in the EFEM and the wafer can be delivered therebetween.
Recently, along with the trend toward high integration or miniaturization of semiconductor devices, the effect from moisture, oxygen, particles or the like in the EFEM needs to be minimized. Therefore, there is suggested a technique for circulating nitrogen gas as a purge gas in the EFEM (see Japanese Patent Application Publication No. 2015-146349).
In the technique for circulating nitrogen gas, which is disclosed in Japanese Patent Application Publication No. 2015-146349, it is required to set the interior of the EFEM to an extremely clean nitrogen atmosphere. Therefore, it is required to prevent inflow of oxygen gas or moisture and particles from the load port or from the FOUP.